Sir A. GeiUe — Age of the Earth. 465 



one hnnrlred millions of years would suffice for that portion of 

 the histoi-y which is registered in the stratified rocks of the crust. 

 But if the palaeontologists find such a period too narrow for their 

 requirements, I can see no reason on the geological side why 

 they should not be at liberty to enlarge it as far as they may 

 find to be needful, for the evolution of organized existence on 

 the globe. As I have already remarked, it is not the length of time 

 which interests us so much as the determination of the relative 

 chronology of the events which were transacted within that time. 

 As to the general succession of these events, there can be no 

 dispute. We have traced its stages from the bottom of the oldest 

 rocks up to the surface of the present continents and the floor of 

 the present seas. We know that these stages have followed each 

 other in orderly advance, and that geological time, whatever limits 

 may be assigned to it, has sufficed for the passage of the long stately 

 procession. 



We may, therefore, well leave the dispute about the age of the 

 earth to the decision of the future. In so doing, however, I should 

 be glad if we would carry away from it something of greater 

 service to science than the consciousness of having striven our 

 best in a barren controversy, wherein concession has all to be on one 

 side and the selection of arguments entirely on the other. During 

 these years of prolonged debate I have often been painfully 

 conscious that in this subject, as in so many others throughout 

 the geological domain, the want of accurate numerical data is 

 a serious hindrance to the progress of our science. Heartily do 

 I acknowledge that much has been done in the way of measurements 

 and experiments for the purpose of providing a foundation for 

 estimates and deductions. But infinitely more remains to be 

 accomplished. The field of investigation is almost boundless, for 

 there is hardly a department of geological dynamics over which 

 it does not extend. The range of experimental geology must 

 be widely enlarged, until every process susceptible of illustration or 

 measurement by artificial means has been investigated. Field- 

 observation needs to be supplemented where possible by instru- 

 mental determinations, so as to be made more precise and accurate, 

 and more capable of furnishing reliable numerical statistics for 

 practical as well as theoretical deductions. 



The subject is too vast for adequate treatment here. But let 

 me illustrate my meaning by selecting a few instances where the 

 adoption of these more rigid methods of inquiry might power- 

 fully assist us in dealing with the rates of geological processes 

 and the value of geological time. Take, for example, the wide range 

 of lines of investigation embraced under the head of Denudation, 

 So voluminous a series of observations has been made in this subject, 

 and so ample is the literature devoted to it, that no department of 

 geology, it might be thought, has been more abundantly and success- 

 fully explored. Yet if we look through the pile of memoirs, articles, 

 and books, we cannot but be struck with the predominant vagueness 

 of their statements, and with the general absence of such numerical 



DECADE IV. TOL. VI. NO. X. 30 



